Although internal combustion engines perform well when clean, uncontaminated fuel is supplied to them, a fuel supply can be easily contaminated in various ways even when precautions are taken to keep the fuel clean. In humid environments or in areas of large temperature variations, condensation often forms on the inside of fuel storage tanks and drips down into the fuel, contaminating it. This problem is especially noticeable when small amounts of fuel are kept in large volume tanks. A majority of the volume of the tank in these situations is occupied by moisture laden air, and the percentage of water in the fuel becomes substantial. Moisture may also find its way into fuel supply systems in other ways. In boats or amphibious vehicles, for example, water from the environment may be introduced inadvertently into the fuel supply system when the fuel tank is filled. Additionally, older storage tanks may rust to a degree that permits contaminants to enter.
Due to the delicate nature of the parts required by compression ignition cycle engines, or diesel engines, moreover, it is extremely important that the diesel fuel supplied to the engines be free from high water content.
Since the contamination of fuel with water is common, a number of systems have been developed for separating water from fuel supply systems. A major problem faced by all of these systems is the elimination of contaminants without admitting other contaminants, such as air, into the fuel supply system through the water discharge opening. Fuel systems are especially prone to sucking air into the fuel supply lines when a discharge opening is located upstream of the fuel pump. Since this opening is located in an area of negative pressure, such systems require special provisions for overcoming the negative pressure before contaminants can be discharged.
U.S. Pat. No. 3,386,581 to Gough discloses an apparatus which may be used to drain water from a fuel tank. Gough, however, provides no apparatus for pressurizing the water separating apparatus before opening the outlet valve used to drain the water from the tank. As a result, the valve must be opened against the force of a vacuum, and air will be drawn into the vacuum when the valve is opened.
U.S. Pat. Nos. 4,495,069 and 4,539,109 to Davis disclose an automatic control means for automatically actuating a drain device in response to the detection of a predetermined quantity of water in a discharge chamber and then deactuating the drain device in response to the detection of a second lower quantity of water in the discharge chamber. In one embodiment of the Davis system, a pump is incorporated in a solenoid-operated discharge valve to overcome negative pressure at the exit of a canister from which water or other impurities are discharged. This additional pump, however, could increase significantly the cost and amount of labor required to manufacture the canister. Furthermore, by providing a pump only at the exit from the canister, the exit pump creates a vacuum opposing the vacuum already in the canister induced by the injection pump. The opposing vacuums may disrupt the flow of fuel to the engine, or, at least, slow down the draining procedure.
U.S. Pat. No. 4,500,425 to Thornton et al. discloses a hand-operated pump mounted upstream from a water separation unit. The pump is used to force fuel into a canister when a sump is drained in order to force out water that has collected in the sump. The hand-operated pump of Thornton et al., however, does not automatically discharge fluid during engine operation. The vehicle must first be stopped so that the plunger of the hand-operated pump can be operated manually to remove the contaminating water.
U.S. Pat. No. 4,334,989 to Hall discloses an automatic fuel-water separator and discharge device which employs a probe to sense water level. When the water level in the separator reaches the level of the probe, a solenoid is activated to force water out of a lower pump chamber. The Hall patent, however, does not disclose a pump upstream of the fuel-water separator or any other structure to overcome a negative pressure in the separator. Furthermore, the Hall device has only one probe; it therefore cannot detect when all of the water has been discharged. As a result, some quantities of fuel may be wasted because fuel is inadvertently discharged with the water. Finally, while the Hall device may work well for discharging small amounts of water, the repeated reciprocation of the plunger mechanism required to discharge large quantities of water could result in problems such as the development of leaks around the periphery of the plunger.
The available prior art systems for separating water from fuel, therefore, use supplemental pumps and pressurizing devices which add unnecessary manufacturing expense and vehicle weight. Additionally, the prior art systems also use small, inexpensive pressurization devices incapable of handling large volumes of water.
In short, no apparatus is known for automatically discharging desired quantities of water from the fuel supply of an internal combustion engine wherein existing fuel system structures are used to allow the automatic decontamination of the fuel supply while the engine is operating.